Update spl module parameters man5 with missing parameter details

Update spl module parameters man5 with the following missing parameter
details for spl_panic_halt.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com>
Closes #664

man/man5/spl-module-parameters.5

@@ -2,7 +2,7 @@
 .\"
 .\" Copyright 2013 Turbo Fredriksson <turbo@bayour.com>. All rights reserved.
 .\"
-.TH SPL-MODULE-PARAMETERS 5 "Nov 18, 2013"
+.TH SPL-MODULE-PARAMETERS 5 "Oct 28, 2017"
 .SH NAME
 spl\-module\-parameters \- SPL module parameters
 .SH DESCRIPTION
@@ -250,6 +250,20 @@ may be overridden for non-standard configurations.
 Default value: \fB/etc/hostid\fR
 .RE
 
+.sp
+.ne 2
+.na
+\fBspl_panic_halt\fR (uint)
+.ad
+.RS 12n
+Cause a kernel panic on assertion failures. When not enabled, the thread is 
+halted to facilitate further debugging.
+.sp
+Set to a non-zero value to enable.
+.sp
+Default value: \fB0\fR
+.RE
+
 .sp
 .ne 2
 .na